The heart is the center of a person's circulatory system. The left portions of the heart, including the left atrium (LA) and left ventricle (LV), draw oxygenated blood from the lungs and pump it to the organs of the body to provide the organs with their metabolic needs for oxygen. The right portions of the heart, including the right atrium (RA) and right ventricle (RV), draw deoxygenated blood from the body organs and pump it to the lungs where the blood gets oxygenated. These mechanical pumping functions are accomplished by contractions of the heart. In a normal heart, the sinoatrial (SA) node, the heart's natural pacemaker, generates electrical impulses, called action potentials, that propagate through an electrical conduction system to various regions of the heart to cause the muscular tissues of these regions to depolarize and contract. The electrical conduction system includes, in the order by which the electrical impulses travel in a normal heart, internodal pathways between the SA node and the atrioventricular (AV) node, the AV node, the His bundle, and the Purkinje system including the right bundle branch (RBB, which conducts the electrical impulses to the RV) and the left bundle branch (LBB, which conducts the electrical impulses to the LV). More generally, the electrical impulses travel through an AV conduction pathway to cause the atria, and then the ventricles, to contract.
Cardiac arrhythmias occur, for example, when the SA node fails to generate the electrical impulses at a normal sinus rate, when a portion of the electrical conduction system is partially or completely blocked, when a pathological conduction loop is formed in the heart, and/or when a pathologically formed electrical focus generates electrical impulses from the ventricles. Heart failure occurs when the myocardium (heart muscles) deteriorates to a degree that significantly impairs the heart's mechanical pumping functions. Electrical signals such as intracardiac electrograms sensed from the heart are used to monitor such conditions. Pacing and cardioversion/defibrillation therapies are applied to treat arrhythmias and heart failure by delivering electrical pulses to the heart. Accuracy in diagnosing cardiac conditions using a device and efficacy of many pacing and cardioversion/defibrillation therapies depend on the understanding of various cardiac events in the sensed electrical signals. Therefore, there is a need for providing accurate detection and recognition of these cardiac events.